On an uplink, that is, a link from a terminal to a base station, in a wireless communication system, a mobile terminal, for example, a user equipment (User Equipment, UE), needs to determine power for transmitting a signal, so that the power remains at a level suitable for reception by the base station when the signal sent by the mobile terminal arrives at the base station, for example, an evolved Node B (Evolved Node B, eNB). The determined power is transmit power.
When determining transmit power of an uplink signal, the mobile terminal specifically obtains the transmit power of the uplink signal according to its maximum transmit power, a measured downlink path loss, a power value expected by a serving base station for receiving a signal and notified by the serving base station, and the like, and transmits the uplink signal to the base station by using the power. After receiving the uplink signal, the base station feeds back a closed-loop power control compensation value to the mobile terminal, so that the mobile terminal adjusts the transmit power according to the closed-loop power control compensation value.
In the prior art, each cell has only one macro base station (that is, a primary base station) for receiving a signal sent by a served mobile terminal. In other words, an uplink signal is independently received by a serving base station in a cell where a mobile terminal is located, and transmit power of the uplink signal also only needs to be controlled to meet a power requirement for independent reception by the serving base station. That is, power control of the uplink signal aims at making the power to be at a level suitable for reception by a primary base station when the signal arrives at the primary base station.
With development of technologies, some new network topology structures make power control of an uplink signal no longer be able to meet various requirements. For example, in a cell, in addition to a macro base station, a plurality of micro base stations are deployed for jointly covering the entire cell. The micro base stations are used to cover hot-spot regions. The macro base station and the micro base stations are connected using high-speed optical cables, facilitating information interaction between them.
In addition, the macro base station in the cell and a macro base station in another cell may jointly receive a signal.
When a mobile terminal transmits an uplink signal, the uplink signal may be received by different base station sets. Existing methods for controlling transmit power of an uplink signal cannot meet requirements of a plurality of receiving manners.
For example, with respect to SRS reception, an SRS is an uplink reference signal transmitted by a terminal side to a base station side and used for channel measurement between a terminal and a bases station. The SRS can not only be used for measurement of an uplink channel but also be used for measurement of a downlink channel. However, with respect to a same terminal, a base station set (referred to as a set A below) for transmitting a downlink signal to the terminal may be different from a base station set (referred to as a set B below) for receiving an uplink signal from the terminal. In this way, if the SRS is used to perform measurement of an uplink channel, the set B receives the SRS, and power control should be adjusted according to a reception level of the set B; whereas if the SRS is used to perform measurement of a downlink channel, the set A receives the SRS, and the power control should be adjusted according to a reception level of the set A. In the prior art, only one power control process is employed, and therefore a power requirement for joint reception by a plurality of base stations cannot be met.
In addition, analogously, in a wireless communication system, time for a terminal side to transmit an uplink signal is controlled by a base station side, so as to achieve an optimal reception effect. In the prior art, when each individual cell has only one macro base station (that is, a primary base station) for receiving a signal sent by a served mobile terminal, the mobile terminal reserves a time advance (Time Advance, TA) value, and transmits an uplink signal to the macro base station at the time point TA.
However, with respect to a new network topology structure where an uplink signal of a mobile terminal may be jointly received by a plurality of base stations, existing time control methods for the uplink signal cannot meet time control requirements of a plurality of receiving manners